Scroll Liquid Pump

ABSTRACT

An orbiting scroll having three sets of wraps is combined on a fixed scroll having three sets of wraps integral to a frame facing each other. The orbiting scroll is adhered on the fixed scroll by the discharge pressure acted to a part of the backside of the orbiting scroll. The orbiting scroll is finely movable to the radial direction and the wraps of the both scrolls contact each other. Thereby it provides a scroll liquid pump that increases the pressure and carries the liquid refrigerant or oil.

PRIORITY

This application claims priority to Japanese Patent Application JP2012-264815 filed Dec. 3, 2012 which application is incorporated by reference herein in its entirety.

BACKGROUND

The present invention relates to a scroll liquid pump for liquids such as liquid refrigerant or oil.

A scroll liquid pump is proposed whose fixed scroll and orbiting scroll have multiple set of fixed wraps and orbiting wraps as described in International publication number WO2010/013351. An orbiting scroll orbits while its rearside is fixed to the orbiting shaft. A fixed scroll is placed movable in an axial direction. Due to the difference of the load by the pressure of the pumping chambers and the load by the discharge pressure of the rearside, the fixed scroll is pushed to the orbiting scroll, the end surface of the orbiting wraps and the floor of the fixed wraps are sealed, and the end surface of the fixed wraps and the floor of the orbiting wraps are sealed. The seal between the intake chamber (fixed body) to which fluid flows and the outside is performed by an outer peripheral wall (moving body). Since the sealing of the fluid is made between the fixed body and the moving body, the leakage of the fluid is not zero. When the outside is outside air, the fluid leaked from the sealing part outflows to the outside. When the scroll liquid pump is lubricated by oil and the outside is a space of the drive part, the fluid leaked from the sealing part flows to the space of the drive part, and dilutes the lubricant oil resulting in the lubrication failure of bearings. The orbiting scroll being fixed to the orbiting shaft cannot move to the location shifted from the turning radius of the orbiting shaft. Therefore the radial clearance gap between the orbiting wraps and the fixed wraps cannot be zero resulting in the insufficient sealing of the pumping chambers.

SUMMARY

1. Technical Problem

The present invention addresses the aforementioned problem and an object of the present invention is to provide a scroll liquid pump having high sealing properties of the pumping chambers by preventing the leakage of the liquid leaked from the clearance gap between orbiting wraps and fixed wraps from leaking to the outside air or drive part, and by reducing any radial gap between the orbiting wraps and fixed wraps to almost zero.

2. Technical Solution

An orbiting scroll having three sets of orbiting wraps is combined to the fixed scroll integral with the frame having 3 sets of fixed wraps facing each other. Pumping chambers are formed by each wrap part. A primary bearing is placed on the center part of the fixed scroll. A secondary bearing is placed in the bearing housing integral to the fixed scroll. A rotating shaft is provided having a crank shaft supported by the primary bearing and the secondary bearing. An orbiting bearing housing open to the surface of the tip side of the orbiting wraps is placed in the center part of the orbiting scroll. An orbiting bearing is provided in the orbiting bearing housing. The orbiting bearing is fitted to the crank shaft.

A rotary ring is mounted on the crank shaft. The rotary ring has an elongate hole. The crank shaft has a flattened part fitted by loose fitting into the elongate hole. The rotary ring is finely movable in a direction of a center axis of the elongate hole against the crank shaft. The elongate hole of the rotary ring and the flattened part of the crank shaft have a receding angle against the rotating direction.

Outlet ports are placed in the center part of the orbiting wraps provided in the orbiting scroll. Seal members are provided on the location of the diameter similar to the outer diameter of the each orbiting wraps on the opposite side of the orbiting wraps. The pressure of the fluid discharged from the outlet ports is exerted in the inner space of the seal members.

ADVANTAGEOUS EFFECTS

Intake chamber 1 a communicates only with inlet port 4 and is blocked from the other parts. So the fluid is not leaked from the intake chamber to the outside or to the space of the drive member. The orbiting scroll 3 is pressed against the fixed scroll 2 with small force so that the gap is almost zero in a radial or axial direction resulting in the improved sealing properties and higher volumetric efficiencies of the scroll liquid pump. Since the pressing force is a small force, the scroll liquid pump has less mechanical loss and less wearing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a scroll liquid pump according to an embodiment of the present invention.

FIG. 2 is a plane view of the fixed scroll of the scroll liquid pump of FIG. 1. FIG. 3 is a plane view of the orbiting scroll of the scroll liquid pump of FIG. 1.

FIG. 4 is a cross-sectional view when the fixed wraps and the orbiting wraps of the scroll liquid pump of FIG. 1 are configured to overlap each other.

FIG. 5 is a cross-sectional view of the orbiting bearing part of the scroll liquid pump of FIG. 1.

FIG. 6 is the plane view of the inner cover of the scroll liquid pump of FIG. 1. FIG. 7 is the result of a load simulation when a receding angle θ of the crank shaft is 12°.

FIG. 8 is the result of a load simulation when a receding angle θ of the crank shaft is 14°.

FIG. 9 is the result of a load simulation when a receding angle θ of the crank shaft is 20°.

DETAILED DESCRIPTION First Embodiment

A fixed scroll 2 is provided integrally with frame 1 as shown in FIG. 1. A housing 10 is installed at the rear of frame 1. A primary bearing 11 is provided in the frame 1. A secondary bearing 12 is provided in the housing 10. A rotary shaft 13 is rotatably supported by primary bearing 11 and secondary bearing 12. A crank shaft 13 a whose shaft center is eccentric is attached on the end of the rotary shaft 13. As shown in FIG. 5, the crank shaft 13 a has a flattened part 13 b and is fitted into an elongate hole 7 a of a rotary ring 7 by loose fitting. The long dimension of the elongate hole 7 a is slightly larger than the long dimension of the flattened part 13 b. Rotary ring 7 hence can move slightly to the longer axis direction of the elongate hole 7 a while rotating with respect to the flattened part 13 b. A centerline 13 c is the centerline of the elongate hole 7 a and the flattened part 13 b. The centerline 13 c is tilted as to have a receding angle θ of a predetermined magnitude against the rotating direction 13 d from the line connecting to the center of rotary shaft 13 and the center of the flattened part 13 b. As shown in FIG. 1, an outer cover 14 is mounted on the outside of an inner cover 8. The outer cover 14 has an outlet chamber 14 a where the fluid flowing out from communicating ports 8 a is retained. An outer cover 14 has a discharge port 14 b that discharges the fluid to the outside. To maintain the rotation balance with the eccentric mass, a primary balance weight 15 and a secondary balance weight 16 are mounted on the rotary shaft 13.

As shown in FIG. 2, three fixed wraps 2 a are erected on the fixed scroll 2. The adjacent fixed wraps 2 a are arranged at angle intervals of 120°, and their phases are shifted from one another by a 120°. A seal wall 2 b is placed on the outer peripheral part of the fixed scroll 2. An inlet port 4 is placed on the fixed scroll 2. An intake chamber 1 a communicating with the inlet port 4 is placed inside of the frame 1 of FIG. 1.

The orbiting scroll 3 of FIG. 3 is placed facing the fixed scroll 2 of FIG. 2. Three orbiting wraps 3 a are erected on the orbiting scroll 3. The adjacent two orbiting wraps 3 a are arranged at angle intervals of 120°, and their phases are shifted from one another by a 120°. Outlet ports 3 b are placed in the center of the orbiting wraps 3 a.

The fixed wraps 2 a and the orbiting wraps 3 a are combined as shown in FIG. 4, and form pumping chambers 5 as shown in FIG. 1. An orbiting bearing 6 is placed in the center of the orbiting scroll 3. A rotary ring 7 is fitted in the orbiting bearing 6.

An oval elongate hole 7 a is placed in the rotary ring 7 as shown in FIG. 5.

An inner cover 8 is placed on the rearside of the orbiting scroll 3. Communicating ports 8 a communicating with outlet ports 3 b of the orbiting scroll 3 are placed. Seal grooves 8 b are placed around the communicating ports 8 a. Ring shaped seal members 9 (in FIG. 1) are mounted in the seal grooves 8 b. Seal members 9 are adhered on the backside of the orbiting scroll 3, and seal the difference of the internal and the external pressure.

The operation is described. A rotary shaft 13 rotates driven by the motor. Accordingly, a crank shaft 13 a rotates. The crank shaft 13 a rotates a rotary ring 7. A rotary ring 7 drives an orbiting bearing 6 and eccentrically turns an orbiting scroll 3. Pumping chambers 5 move from the outer peripheral side toward the center side reducing the volume by the eccentric movement. The fluid is sucked from an inlet port 4, flows via an intake chamber 1 a, and is pushed into the inner peripheral side of the pumping chambers 5. Then, the fluid force acts on orbiting scroll 3 from the opposite side of the orbiting direction. As shown in FIG. 5, the fluid force acts as the tangential fluid force Ft of the orbiting bearing 6 and the rotary ring 7. A crank shaft 13 a has a flattened part 13 b. The crank shaft 13 a tilts so that the centerline 13 c of the flattened part 13 b has a receding angle θ against rotating direction 13 d. A radial force Ftr is produced on the rotary ring 7 as a component force of the tangential force Ft since the rotary ring 7 is movable along the centerline 13 c. Radial force Ftr pushes the orbiting scroll 3 to the direction that the turning radius becomes greater.

A radial fluid force Fr acts toward an inside of the radial direction of the orbiting scroll 3 when the scroll liquid pump is operated. A centrifugal force Fc occurs in the orbiting scroll 3 toward the outside in the radial direction. When the orbiting scroll orbits in low speed, the radial fluid force Fr may be greater than the centrifugal force Fc. At this time, the orbiting scroll 3 is pushed by a smaller force by the resultant force toward the radial direction outside when the receding angle θ is set so that the radial force Ftr is slightly greater than the difference of the radial fluid force Fr and centrifugal force Fc. For this reason, the orbiting wraps 3 a move until they contact the fixed wraps 2 a thereby the clearance in the radial direction is almost 0. Therefore the sealability of the pumping chambers 5 is improved.

FIG. 7 is the simulation result of the radial force Ftr and radial fluid force Fr when the receding angle θ is set to 12°. Since each of the radial fluid force (not shown) of three pumping chambers 5 is almost constant regardless of the phases of orbiting wraps 3 a and fixed wraps 2 a, the radial fluid force Fr integrated by 3 sets of pumping chambers is almost constant value. Whereas, the radial force Ftr integrated by three sets of pumping chambers fluctuates at a cycle of phase difference of fixed wraps 2 a and orbiting wraps 3 a, since each radial force (not shown) of pumping chamber 5 fluctuates within one cycle. In the First Embodiment, a radial force Ftr fluctuates at a cycle of 120° since the phase difference is 120°. On the average, radial force Ftr exceeds radial fluid force Fr, although there may be times that a radial force Ftr may be less a little than a radial fluid force Fr during one cycle when a receding angle θ is 12°. So the 12° of a receding angle θ is the lower-limit value.

FIG. 8 shows the simulation result of a radial force Ftr and a radial fluid force Fr when a receding angle θ is set to 14°. The 14° of a receding angle θ is an optimal value since a radial force Ftr always exceeds a radial fluid force Fr during one cycle.

FIG. 9 is the simulation result of a radial force Ftr and radial fluid force Fr when a receding angle θ is set to 20°. The orbiting wraps 3 a can be sufficiently adhered on the fixed wraps 2 a since the average value of the radial forces Ftr is the twice of the radial fluid force Fr during one cycle. On the other hand, it is not desirable to exert the radial force Ftr more than this, because the orbiting wraps 3 a are pressed to the fixed wraps 2 a by the greater force than the radial fluid force Fr and the contact pressure becomes excessive resulting in the friction loss or the increase in wear. Therefore, 20° of a receding angle θ is the upper limit.

Based on the above evaluation, it is desired to set a receding angle θ in a range of 12° to 20°.

The pressures inside of pumping chambers 5 are equal to the discharge pressure. The cross-section area in the plane direction of pumping chambers 5 is the largest at the start of an intake, and is the minimum at the end of the discharge. In proportion to this cross section, the discharge pressure inside of the pumping chambers 5 produces the force to detach the orbiting scroll 3 from the fixed scroll 2. The pressure of the orbiting scroll backside is the discharge pressure. The area that the discharge pressure works is the area inside of the seal members 9. The inside area determines the diameter of the seal members 9 so that pumping chambers 5 are slightly bigger than the maximum cross sectional area of the horizontal direction at the start of the intake. By this, the orbiting scroll 3 is pressed against the fixed scroll 2 with a small force by a pressure difference. So, the gap in an axial direction becomes almost zero thereby improving the sealability of the pumping chambers 5.

The fluid pushed toward the inner periphery of the pumping chamber is discharged to the outside from the discharge port 14 b via outlet ports 3 b, communicating ports 8 a, and outlet chamber 14 a. A self-rotational torque is produced at the orbiting scroll 3 by the fluid force to the same direction as the rotating direction 13 d of the rotary shaft 13. However, the self-rotation of the orbiting scroll 3 is prevented because the fixed wraps 2 a and the orbiting wraps 3 a are 3 sets at a 120° interval, and the self-rotational force of the orbiting scroll 3 is received by any of the wrap contact areas of the three sets of fixed wraps 2 a and orbiting wraps 3 a. So, a self-rotation prevention mechanism exclusive to the scroll liquid pump is not necessary. 

1. A scroll liquid pump, wherein an orbiting scroll having three sets of orbiting wraps is combined to the fixed scroll having three sets of fixed wraps facing each other, such that a pumping chamber is formed by each pair of orbiting and fixed wraps; a primary bearing is placed on the center part of the fixed scroll; a secondary bearing is placed in a bearing housing integral to the fixed scroll, a rotary shaft is provided supported by the primary bearing and the secondary bearing, the rotary shaft carrying a crank shaft; an orbiting bearing housing open to the surface of the orbiting scroll on which the orbiting wraps are carried is placed in the center part of the orbiting scroll; an orbiting bearing is provided in the orbiting bearing housing; and the orbiting bearing is fitted to the crank shaft.
 2. The scroll liquid pump according to claim 1, wherein a rotary ring is mounted on the crank shaft; the rotary ring has an elongate hole; the crank shaft has a flattened part fitted by loose fitting into the elongate hole; the rotary ring is finely movable in a direction of a long axis of the elongate hole against the crank shaft; the long axis of the elongate hole of the rotary ring and of the flattened part of the crank shaft make a non-zero receding angle with a line joining the centre of the crank shaft and the centre of the rotary shaft against the rotating direction.
 3. The scroll liquid pump according to claim 1, wherein outlet ports are placed in the center part of the orbiting wraps provided in the orbiting scroll; seal members are provided on the location of the diameter similar to the outer diameter of the orbiting wraps on the opposite side of the orbiting wraps; the pressure of the fluid discharged from the outlet ports is exerted in the inner space of the seal members. 